In recent years, along with an increase in the recording capacity of a hard disk drive, densification for a high recording density has been in progress at a high pace. However, along with the densification for a high recording density, microfabrication of magnetic particles is likely to impair thermal stability, thus leading to a problem of cross talk or a decrease in the S/N ratio of a playback signal. Under the circumstance, attention has been drawn to a thermal assist magnetic recording technique as a combined technique of optics and magnetism. This is a technique wherein a magnetic recording layer is irradiated with a laser beam or near field light to lower the coercive force locally at the heated portion, and in such a state, an external magnetic field is applied for recording, and the recorded magnetization is retrieved by e.g. GMR element, whereby recording can be made on a high coercive force medium, and it becomes possible to microfabricate magnetic particles while maintaining the thermal stability. However, in order to form a high coercive force medium in the form of a multi-layered film, it is required to sufficiently heat the substrate, and a highly heat resistant substrate is desired.
Further, also for a perpendicular magnetic recording system, a magnetic recording layer different from a conventional one has been proposed in order to meet the requirement for densification for a high recording density, but for the formation of such a magnetic recording layer, the substrate is required to be heated at a high temperature, in many cases.
Whereas, a silicon substrate has been proposed as a substrate which is useful for the above mentioned thermal assist magnetic recording technique (Patent Document 1).